{"id":"CVE-2026-62949","title":"AsyncSSH is a Python package which provides an asynchronous client and server implementation of the SSHv2 protocol on top of the Python asyncio framework","summary":"AsyncSSH is a Python package which provides an asynchronous client and server implementation of the SSHv2 protocol on top of the Python asyncio framework. Prior to 2.24.0, _process_channel_open and _process_channel_open_confirmation in a…","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-835"],"vendor":"ronf","product":"asyncssh","affected":["asyncssh < 2.24.0"],"patched":["asyncssh 2.24.0"],"published":"2026-09-16","updated":"2026-09-17","sourceUpdated":"2026-09-17T16:17:34.413","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-62949","references":[{"url":"https://github.com/ronf/asyncssh/commit/756cbae5350789ce9735f15f704bae9b5a3608b8","label":"security-advisories@github.com"},{"url":"https://github.com/ronf/asyncssh/commit/9c354270c009285525e126721e8ed5fbed1f8a67","label":"security-advisories@github.com"},{"url":"https://github.com/ronf/asyncssh/releases/tag/v2.24.0","label":"security-advisories@github.com"},{"url":"https://github.com/ronf/asyncssh/security/advisories/GHSA-rw4j-r22c-9gc3","label":"security-advisories@github.com"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-62949"},{"url":"https://github.com/advisories/GHSA-rw4j-r22c-9gc3"},{"url":"https://github.com/ronf/asyncssh"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-62949.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-62949"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2535643"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-62949"}],"tags":["nvd","cve.org","ghsa","pip","osv","csaf","vex","red-hat"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-09-17T15:01:41.382412Z"},"aliases":["GHSA-rw4j-r22c-9gc3"],"ecosystem":"pip","ingestedAt":"2026-09-16T21:05:36.875Z","epss":0.00548,"epssPercentile":0.43454,"slug":"CVE-2026-62949","body":"## Overview\n\nAsyncSSH is a Python package which provides an asynchronous client and server implementation of the SSHv2 protocol on top of the Python asyncio framework. Prior to 2.24.0, _process_channel_open and _process_channel_open_confirmation in asyncssh/connection.py accept a peer-supplied send_pktsize value of zero. When channel data reaches SSHChannel._flush_send_buf in asyncssh/channel.py, the zero value causes each loop iteration to slice and remove zero bytes without reducing the send window, leaving the synchronous loop permanently true with no await point. A malicious SSH server can trigger the client path through SSH_MSG_CHANNEL_OPEN_CONFIRMATION before the first channel write, while an authenticated client can trigger the server path through SSH_MSG_CHANNEL_OPEN and freeze every current and future connection handled by the process. This vulnerability is fixed in 2.24.0.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-62949)\n\nAffected packages:\n\n- `asyncssh <= 2.23.1`\n\nPatched in:\n\n- `asyncssh 2.24.0`\n\nSource: https://github.com/advisories/GHSA-rw4j-r22c-9gc3\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Ceph Storage 7, Red Hat Ceph Storage 8, Red Hat Ceph Storage 9 · no fix planned: Red Hat Ceph Storage 7, Red Hat Ceph Storage 8, Red Hat Ceph Storage 9 · updated 2026-09-23 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-62949.json)","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}